P112

[Fred Cisin]

On Sun, 1 Dec 2019, Bill Gunshannon via cctalk wrote:
> Well, I haven't tried 5.25" but 3.5" disks format/read/write just fine.

That is a significant succesful test of MOST of the hardware.
(leaving drive, cabling, and software as the likely alternate culprits)

Speculating (with no knowledge of P112 (or P118 :-)) about the wrong 
parameters (even though 77 V 80 SEEMS minor), if the parameters are 
stored separately for FORMAT V READ/WRITE, that could obviously do it. 
If it were to have totally wrong parameters, and tried to put more 
sectors on a track than would fit, would it wrap around (past index) and 
overwrite the first sector with one of the later ones?


A couple of obvious other things to consider (that you probably 
have already considered) trying:
1) do you have some other machine with 8" capability to look at the disk 
that you formatted?

2) Do you get the same errors on a pre-formatted disk from something else?
(not necessarily much good as a test, because any format with different 
sector size or sector numbering would probably also give that error)

3) Perhaps tell it that the 3.5" drive is an 8", and see what it does
(300RPM V 360RPM shouldn't prevent that interchange in that direction, 
although "type 3" 3.5" drive (360RPM) would be ideal)